1. Field of the Invention
The present invention relates to a printer and a printing method, in particular a printer and a printing method that make a margin-free print.
2. Explanations of the Prior Arts
Due to the wide usage of digital still camera, demand for color printing of the photographed image is on the increase. A color thermosensitive printer is used for color printing. The color thermosensitive printer has a thermal head to print a full-color image to a color thermosensitive recording paper with yellow, magenta, and cyan thermosensitive coloring layers on a substrate. The color thermosensitive printer heats a heating element array of the thermal head, so that the three thermosensitive coloring layers successively develop their respective colors, to form a full-color image.
It is preferable to have a marginless printing in terms of print efficiency and print quality. In order to make a marginless print, the heating element array must be wider than the color thermosensitive recording paper to record the lateral edge of the color thermosensitive recording paper without fail. When the heating element that does not touch the color thermosensitive recording paper is heated, however, so-called xe2x80x9cwasted heatingxe2x80x9d happens to exceedingly increase the temperature of such heating element. Then the life-time of the heating element is shortened.
In order to prevent the wasted heating, JPA No. 9-272217 discloses a printer having regulation means that corrects the position of a color thermosensitive paper tilted in the width direction. Further, the printer applies inspection light to a lateral edge portion of the color thermosensitive recording paper. A CCD line sensor detects the lateral edge by monitoring inspection light reflected at the color thermosensitive recording paper.
In terms of cost and space, some printers do not have regulation means. Such printer may cause tilt of the color thermosensitive recording paper. As shown in FIG. 9, when a color thermosensitive recording paper 70 is inclined to inclined to the direction of arrangement of a heating element 73 against the width direction, the jaggy areas 72 are appeared on both lateral edge portions of a print image 71 (shown by diagonal line). These jaggy areas 72 lowers image quality.
An object of the present invention is to provide a printer and a printing method that improves image quality by decreasing jaggy effect.
To attain the above object, the printer of the present invention has a record control section to control an edge recording elements of a recording head to decrease the recording density at the lateral edge of a recording paper in a main scan direction. A detecting section specifies an edge recording element that is closest to the lateral edge position among the recording elements with the whole pixel in the recording paper.
In the preferred embodiment, the printer has a CCD line sensor on which plural pixels are arranged in the main scan direction. The pixels of the CCD line sensor and the recording elements are respectively arranged at an equal pitch in the main scan direction. The detecting section detects the lateral edge position by the change of output signal levels from the pixels. The lateral edge position is stored into the memory as lateral edge position data.
The detecting section interpolates the output signal levels from the pixels to obtain an output level curve with respect to said main scan direction. Each time the recording paper is conveyed by one line, the detecting section decides the lateral edge position in which the output level curve takes a set value.
The record control section calculates a control value that is the proportion of the distance between the lateral edge position and the edge recording element in the main scan direction to the interval of the adjacent recording elements. Recording density of the edge pixel is adjusted in accordance with the control value. In order to determine the recording density of the edge pixel, the control value is multiplied by density of the image corresponding to the edge pixel.
As recording density is lowered according to the proportion, the boundary between the edge of the recording paper and the print image is blurred to improve image quality.